Baricitinib is a Janus kinase (JAK) inhibitor. It is chemically designated as {1-(ethylsulfonyl)-3-[4-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)-1H-pyrazol-1-yl]azetidin-3-yl}acetonitrile, having the structure as depicted in Formula I.

U.S. Pat. No. 8,158,616 discloses processes for the preparation of baricitinib of Formula I and [4-(1H-pyrazol-4-yl)-7H-pyrrolo[2,3-d]pyrimidin-7-yl]methyl pivalate of Formula II.

U.S. Pat. No. 8,158,616 involves a three-step process for the preparation of [4-(1H-pyrazol-4-yl)-7H-pyrrolo [2,3-d]pyrimidin-7-yl]methyl pivalate of Formula II as depicted in Scheme 1 below:

The process disclosed in U.S. Pat. No. 8,158,616 involves the use of sodium hydride as a base for reacting 4-chloro-7H-pyrrolo[2,3-d]pyrimidine of Formula III with chloromethyl pivalate of Formula IV, and the use of a protected pyrazole borolane derivative of Formula VI for the conversion of (4-chloro-7H-pyrrolo[2,3-d]pyrimidin-7-yl)methyl 2,2-dimethylpropanoate of Formula V into [4-(1H-pyrazol-4-yl)-7H-pyrrolo[2,3-d]pyrimidin-7-yl]methyl pivalate of Formula II.
The use of sodium hydride is not suitable on an industrial scale due to its inflammable and hazardous nature. The use of a protected pyrazole borolane derivative of Formula VI increases the cost of the manufacturing process, as an additional deprotection step is required for obtaining [4-(1H-pyrazol-4-yl)-7H-pyrrolo [2,3-d]pyrimidin-7-yl]methyl pivalate of Formula II.
Thus, there exists a need for the development of an economical and industrially advantageous process for the preparation of [4-(1H-pyrazol-4-yl)-7H-pyrrolo[2,3-d]pyrimidin-7-yl]methyl pivalate of Formula II that avoids the use of sodium hydride and involves a lesser number of steps.